Huntington's disease (HD) is an autosomal dominant neurodegenerative disorder. Animal studies have demonstrated that impairment of cellular mitochondrial ener-gy metabolism and/ or altered glutamatergic N-methyl-D- asparate recetor-mediated activity can produce neuropathologic changes closely resembling HD. This study will test interventions, coenzyme Q10 and remacemide hydrochloride, that buttress mmitochondrial energy metabolism and attenuate the decline of HD.